Apparatus for stripping and printing motion-picture films with improved registration



May 8, 1951 2,551,68

' A. J. MILLER APPARATUS FOR STRIPPING AND PRINTING MOTION-PICTURE FILMSWITH IMPROVED REGISTRATION Filed Feb. 18, 1949 2 Sheets-Sheet 1 INVENTOR\QW XM, ATTORNEY May 8, 1951 A. .LIMIL 2,551,689

LER APPARATUS FOR STRIPPING AND PRINTING M ION-PICTURE FILMS WITHIMPROVED REGISTR ON Filed Feb. 18, 1949 2 Sheets-Sheet 2 INVENTOR BY WAITTORNEY Patented May 8, 1951 UNITED STATES PATENT OFFICE Arthur J.Miller, Teaneck, N. J.

Application February 18, 1949, Serial No. 77,134

11 Claims. (Cl. 411) contact for a substantial period while the dyeisimbibed, and for stripping a color separation layer which alsoinvolves a substantial period of time to obtain softenin of the bondbetween the color separation layer and the negative from which it is tobe stripped and afiixed to another It is an object of this invention toprovid a improved apparatus for bringing the corresponding frame areasof the superimposed films into accurate registration; and it is anotherobject of the invention to maintain the accurate registration while thefilms move beyond the station at which the original registration wasimposed.

The films are preferably of the same length between sprocket openings atthe time of registration, and feature of the invention relates to thetreating of one film so as to make its length between sprocket openingscorrespond with the length of the other film with which it is to bebrought into contact for the printing or stripping operation. Ordinarilythe film frame lengths of a processed film, such as a developed negativefilm strip, are shorter than the frame areas of a strip of raw filmstock. Even a small difference in the spacings of the sprocket openingsof two films is objectionable when attempting to obtain accurateregistration because the difi-erences in sprocket opening spacings areaccumulative.

With this invention, the film having the shorter spacings betweensprocket tooth openings is passed through a bath, which may be water,with the temperature coordinated with the rate of travel so that thelength of the film will increase and cause the spacings between theopenings to correspond with those of the other film.

Another object of the invention is to bring successive film frame areasinto accurate registration without passing the superimposed films aroundany abrupt turns at either the registration station or immediatelybeyond the registration station. Passage of the film into or out of anabrupt turn causes some creeping of one film across the other because ofth difference in the radius of curvature of the two film strips. Thisinvention passes the films across a sprocket having registration pins orteeth that are retractable, and

that are projected into the sprocket openings 2 and along a substantialrun which is free of abrupt turns.

The sprocket used for this invention, with retractable teeth, is claimedin my copending application Serial No. 1,152, filed January 8, 1948.

Other objects, features and advantages of the invention will appear orbe pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like referencecharacters indicate corresponding parts in all the views.

Figure 1 is a diagrammatic assembly view of apparatus for stripping orprinting motion picture film in accordance with this invention.

Figure 2 is an enlarged view, partly broken away and in section, of theguide means and registration pins at the registration station of Figure1, the section being taken alon the line 2-2 of Figure 3.

Figure 3 is an enlarged sectional view taken on the line 33 of Figure 2.

Figure 4 is a greatly enlarged sectional view showing the operation ofthe sprocket in producing registration of the film strips.

Figure 5 is a greatly enlarged sectional view taken on the line 55 ofFigure 3.

The apparatus shown in Figure 1 includes 'a reel ID that holds anunprocessed film to which one of the color separation emulsions of thenegative is to be transferred. This reel is supported by a bracket IIfrom a main frame l2 of the apparatus. On another reel 15 there is wounda negative film having different color separation emulsions bonded toit.

The reel 15 is supported by a bracket l6 from a tank I! which isconnected with the main frame I2. The film or film strip 20 from thereel l5 passes between feed rolls 2|, one 'of which has sprocket teethwhich engage with sprocket tooth openings in the film strip 28. From thefeed rolls 2|, the film 20 passes around idler rolls 23 and 24 at theupper and lower portions of the tank. I]. There may be a plurality ofcoaxial rolls 23 at the top of the tank and corresponding coaxial rolls24 at the bottom of the tank for obtainin a number of loops of the film20 in the tank ll. This isa well known expedient in the motion pictureart for keeping the film immersed for a substantial period even thoughit is traveling at a relatively rapid linear speed.

The tank I 1 contains liquid that will softe the bond between theoutside color separation emulsion of the film 20 and the next underlyingemulsion. Passing through the liquid in the tank I! causes the film 20to soften and stretch slightly so that the spacings of its sprocketopenings correspond with those of the film from the reel l0.

7 The effectiveness of the liquid in thetank ll depends not only uponthe length of time that the film is in the liquid, but also upon thetemperature of the liquid. Since the speed of travel of the film isdetermined, at least to some extent, by the available distance betweenthe registration station and the apparatus at which the films are movedout of contact with one another beyond the registration station, thetank equipped with coils 23 for controlling the temperature of theliquid in the tank. This temperature is coordinated with the speed offilm travel so as to obtain the desired increase in film length.

After passing beyond the last roll 25, the film 20 travels around asprocket 28, and the deflected run of the film around the sprocket 28can be kept under some tension as an aid in stretching the softened filmto the same inter-sprocket opening length as the film 20.

The unprocessed film 30 from the reel l8 passes around a guide roll 33and then upward to a registration station which is indicated generallyby reference character 35. The negative film 20 passes around a guideroll 34 which brings the films 20 and 30 into contact with one anotherimmediately below the registration station 35.

At the registration station 55 there is a sprocket 36 with teeth forengaging the sprocket openings in the superimposed films 2B and 38; andthe films are held against the sprocket 36 by a roll 38 supported by abell crank 39 which rocks about a pivot 40 extending from the main frame02. In order to obtain a uniform pressure between the roll 38 and thefilms 20 and 35; a weight 42 is placed on the horizontally extending armof the bell crank 39. This weight can be adjusted toward and from thepivot 58 to control the pressure exerted by the roll 38.

There are successive pairs of guide rolls 15 and 46 beyond theregistration station 35. These guide rolls 45 and 45 maintain the run ofthe films substantially straight and tangent to the sprocket 36, andsupply a wringing action to press the films tightly into contact as thefilms move beyond the registration station. Feed rolls 41 and 48 pullthe films 20 and 39 through the successive passes between the guiderolls 45 and 46. The roll 48 has teeth for engaging the sprocketopenings in the films.

The sprocket or toothed roller 48 imparts a constant tension to thefilms. This result can be attained by driving the sprocket 48 through afriction clutch, but preferably by mounting the sprocket 48 on a slidemovable in the direction of the films and provided with a counter weightand pulley arrangement to assure the constant tension. Since sprocket 58is driven by a chain, enough slack and a spring loaded idler will driveregardless of slight variations in the length of film between theregistration station and this sprocket.

Beyond the feed rolls 4! and 48, the films 20 Ward from the wheel 50into a frame 53 that holds a tank 54 in which the films are separatedfrom one another. The films 3!! travels around rolls 55 and toward theright hand end of the tank 5 whereas the other film travels around rolls55 and toward the left hand end of the tank 54. The tank 55 is filledwith water to a level above the region at which the films 20 and 39 moveout of contact with one another. The actual stripping of th emulsion isthus carried on under water.

Within the frame 53, the separate films 30 and 23 travel up and downaround rolls 55 and 58, respectively; and pass adjacent to spray nozzles59 from which water is projected to wash the The distance that the films20 and 35 travel from. the registration station 35 to the stripping tank54 is coordinated with the speed at which the feed rolls are driven soas to allow time for the color separation emulsion bond to soften andfor the emulsion to adhere firmly to the film 30 to which it is beingtransferred.

The films 20 and 30 pass from the guide rolls in the frame 53 to otherguide rolls in dryers 6B and 6!, the film 20 being dried in the dryer 6|and the film 30 being dried in the dryer 60. Beyond the dryers, thefilms 20 and 38 are wrapped around reels 62 and 63 respectively. Thesereels are driven by any conventional wind-up mechanism, the illustrationof which is not necessary for the complete understanding of thisinvention.

In order to obtain accurate control and coordination of the speed of allof the feed rolls, power is preferably supplied to all driven rolls froma common motor. In the illustrated construction, an electric motor 65drives a speed reducer 65 through a belt 61. A sprocket 69 at the lowspeed end of the speed reducer 66 drives a chain H1 through which poweris transmitted to a. shaft H. The sprocket 36' is secured to the shaftH, and there are other sprockets 13 also secured to the shaft fordriving chains 14 through which power is transmitted to the feed rolls2!, 51

. v and 48.

' 3!! extending between sprockets on the ends of and 30 pass around alarge wheel 5!] supported by axle 5! from the main frame H2. The radiusof the wheel is so large in proportion to the thickness of the film 25that the percentage difference in the radii of curvature of the films 25and 30, when passing over the wheel 50, is so small the shafts to whichthese rolls is are secured.

The apparatus shown in Figure 1 can also be used for imbibition colorprinting where accurate registration and the maintaining of suchregistration is highly important. When used for imbibition printing, thematrix is wrapped around the reel l 5 and is advanced exactly the sameway' as the film strip 30, but the tank I1 is filled with a liquid dyeinstead of the emulsion bond solvent employed when the apparatus is usedfor stripping.

The apparatus is also suitable for making black and white prints, butthe maintaining of accurate registration is not necessary after thefilms for such prints pass an exposure station located at theregistration station 35. When making black and white prints, thenegative film is wound on the reel I5 and the tank I! is filled withwater. By passing the negative through water at a controlledtemperature, the negative can be made to stretch so that the spacings ofits sprocket openings correspond with those of the "raw'film stock woundon the reel l0.

The registration station 35 with the film guide means, for maintainingthe superimposed film strips substantially tangent to the sprocket 36from which the registration teeth are projected, can be used without thetank I! if the film strips are originally of equal length betweensprocket openings. Unprocessed film strips can be shrunk under properconditions to correspond in sprocket opening spacing with films thathave been processed. When a particular negative is to be printed, a gagecan be used to measure the spacing of its sprocket openings, andunprocessed film for printing or stripping can be gaged and selected forits equal sprocket opening spacing. The feature of this invention bywhich one film is treated to bring its length to that of the other filmhas the important advantage, however, that it permits the invention tobe used with any stock which happens to be available and does notrequire as much inventory.

In the event that the original films are of the same length, and one ofthe films has to be passed through a die or solvent in the tank 11, awater bath can be provided for the film 33 so as to maintain thespacings of the sprocket openings equal. In rare instances where the rawfilm stock has shrunk to such an extent that its sprocket openingspacings are less than those of the processed film with which it is tobe used, the unprocessed film is subject to a greater expansion than theother film by passing it through a warm bath or by having enough loopsof the film in the bath so that it is submerged for a greater length oftime than the other film.

The construction of the sprocket 36 is shown in Figures 2 to 5. Thesprocket comprises a hub 90 and a body portion that includes twoparallel spaced flanges 92 that are preferably integral with the hub 90.Each of the flanges 92 has sprocket teeth around its periphery, and inthe construction shown certain sprocket teeth 84 are integral with theflange 92, whereas other sprocket teeth 95 are movable in a radialdirection. Every fourth tooth is a movable tooth in the structureillustrated.

Since standard motion picture film has four sprocket openings for eachfilm frame area, the construction with every fourth tooth movableprovides a movable sprocket tooth 95 for each film frame area. Thesemovable sprocket teeth serve as registration pins for bringing the frameareas of the films 2D and 3i) into accurate registration for printing orstripping.

Each of the movable teeth or pins 95 slides in a guide slot (Di in theadjacent flange 92 and a;

the movable teeth or pins 95 are held in their guide slots by aretaining ring I03 that is attached to the flange 92 by screws H14. Thelower end of each of the movable teeth or pins 95 has a downwardlyextending projection I66 that is located radially inward from the flange92, and that fits into a slot I01 of a cam I08.

There is a cam 108 on each side of the sprocket, and each cam I08 isrigidly secured to a stationary supporting structure 1 l8. or pins 95are preferably of rectangular section and the slots i: are ofsubstantially similar cross section and provide bearing surfaces inwhich the pins 95 are free to slide while being held against turning inthe guide slots lill. The projection 196 at the lower end of each of themovable teeth or pins 95 serves as a cam follower and is preferably ofcircular cross section.

The cam slot lll'l is circular around most of its extent and has itscenter of curvature on the axis The movable teeth of rotation of thesprocket. The cam slot I01 departs from its circular curvaturethroughout the relatively small length of its circumference immediatelyunder the roll 38. By having the high part of the cam slot 10'! ofshorter effective length than the frame areas of the films, the movableteeth of the sprocket 3B impose registration on only one pair ofsuperimposed frame areas at a time. This feature makes it possible toobtain accurate registration ven though there are some slightdifferences in the spacing between the sprocket openings of the twofilms. When the apparatus is used for printing a positive film byexposure to light through a negative film, the exposure station can belocated at any desired region between the registration station and theupper feed rolls 41' and 48.

Figure 4 shows the shape and operation of the movable teeth or pins 55,and illustrates also the way in which the films 2B and 30 are advancedby the integral sprocket teeth 94. The clearances around the sprocketteeth in the sprocket openings of the films are exaggerated in Figure 4for clearer illustration.

It will be apparent from Figure 4 that the integral sprocket teeth 94contact with the forward edges of the sprocket openings in the films 29and 33 to advance the films in accordance with the rotation of thesprocket 36. These teeth $4 fit loosely in the sprocket openings andtherefore do not maintain the film frame areas in register. The teeth 95have tapered upper ends that fit loosely in the sprocket openings of thefilms while the positions of these movable teeth or pins 95 are underthe control of the circular portion of the cam track I01.

As each pin 95 approaches the registration station, the pin is thrustradially outward into the position of the upper pin 95 in Figure 4, andwhen in this position, the pin 95 fits snugly in the sprocket openingsof the films 2!] and 3E! and compels registration of the film frameareas at the region of tangency of the films 20 and 3!! with thesprocket 36. As the pin 95 travels beyond the region of tangency, it ispulled inward again by the shape of the cam track [07.

It is a feature of the invention that the films 2i and 3B aresubstantially tangent to the sprocket 36, and it is another feature ofthe invention that the sprocket 36 imposes registration on only one filmframe area at a time.

The preferred embodiments of the invention have been illustrated anddescribed, but changes and modifications can be made and some featurescan be used alone or in different combinations without departing fromthe invention as defined in the claims.

What is claimed is:

1. Apparatus for treating motion picture film strips having sprocketopenings, said apparatus comprising a device for treating a film stripto make its length between sprocket openings substantially equal to thatof another film strip, guide means that bring the film strips intoinitial contact with one another, a registration station immediatelybeyond the region at which the film strips are brought into contact withone another, guiding means between which the two film strips pass at theregistration station with the film strips in contact with one anotherand with at least one surface of the guiding means in contact with oneof the film strips and movable with the film strip, retractableregistration teeth in the surface of the guide means that moves with thefilm strip, mechanism that moves the retractable registration teethselectively into and out of full engagement with sprocket openings ofthe film strips as successive portions of the film strip reach theregistration station, said registration teeth being of a size to engagefully the sprocket openings of the film strips for compelling accurateregistration of frame areas of the respective film strips, and otherguide means for the film strips beyond the registration station withcontact surfaces that guide the strips without aifecting theregistration imparted to the film strips by the retractable teeth.

2. Treating apparatus for motion picture films having corresponding rowsof sprocket openings, said apparatus comprising a device for treatingone film to make its length between sprocket openings substantiallyequal to that of the other film, guide means that bring the film stripsinto initial contact with one another, a station immediately beyond saidguide means at which successive film frame areas of the respective filmsare brought into accurate registration, guiding means at theregistration station including a sprocket that turns to advance thefilms, teeth on the sprocket angularly spaced around the periphery ofthe sprocket for engaging the sprocket openings of the films, at leastsome of said teeth being of a size to fit fully in the sprocket toothopenings, means that operate in timed relation with the revolutions ofthe sprocket for projecting and retracting the full fit teeth, and otherguide means for the film strips beyond the registration station withcontact surfaces that guide the strips without afiecting theregistration imparted to the film strips by the retractable teeth.

3. Apparatus for advancing superimposed motion picture film strips withrespect to a registration station, said apparatus including a devicethat treats one film strip to make the length of its respective frameareas correspond to that of the other film strip, guide means that bringthe film strips into initial contact with one another ahead of theregistration station, a guiding means adjacent to the registrationstation, a sprocket associated with said guiding means, registrationteeth angularly spaced around the periphery of the sprocket, saidregistration teeth being of a size to fit fully into the sprocketopenings in the superimposed film strips, cam means that displace theregistration teeth into and out of engagement with the film sprocketopenings as the sprocket turns, said cam means having an effectivedisplacement region shorter than the spacing of the registration teeth.

4. Apparatus for stripping or printing colored motion picture filmstrips having sprocket openings, said apparatus comprising a devicethrough which the shorter of said film strips passes to in crease itslength between sprocket openings to that of the other film, guide meansthat bring the film strips into initial contact with one another, aregistration station through which the film strips pass in superimposedrelation to one another, a sprocket at the registration station, meansthrough which driving power is supplied to the sprocket for advancingthe film strips, said sprocket having teeth an-gularly spaced around itsperiphery for engaging the sprocket openings of the film strips, some ofthe sprocket teeth fitting freely into the sprocket openings and othersof the sprocket teeth being of a size to fit fully into the sprocketopenings and impose exact registration of successive film frame areas,mechanism that moves the full fit teeth radially in the sprocket intoand out of full engagement with sprocket openings in the films aspredetermined openings reach the registration station, and other guidemeans for the film strips beyond the registration station with contactsurfaces that guide the strips Without affecting the registrationirnparted to the film strips by the retractable teeth.

5. Stripping apparatus for color films, including in combination, adevice for increasing the length of a raw film strip, from which a colorseparation layer is to be transferred, so that the spacing of sprocketopenings in the raw film stri is equal to the spacing of correspondingsprocket openings of the other film, a tank of liquid through which saidraw film strip passes to receive an immersion in a liquid that softensthe bond of the color separation layer that is to be stripped, guidemeans that bring the film strips into initial contact with one another,a registration station immediately beyond the region at which the filmstrips are brought into contact with one another, apparatus for movingfull fit registration pins into and out of the sprocket openings ofsuccessive film frame areas as said openings reach the registrationstation, guide means beyond the registration station along which thefilms pass without abrupt turns and without affecting the registrationimparted to the films by the retractable pins, the length of the guidemeans being coordinated with the intended rate of travel of the films toallow time for softening of the bond of the color separation layer, astripping tank that holds liquid through which the films pass, guidemeans that separate the films under the liquid in the stripping tank,and a dryer beyond stripping tank and through which the films pass asthey come from the stripping tank.

6. In film treating apparatus of the class wherein a motion picture filmis passed through a liquid tank to make the spacings of the sprocketopenings equal to those of another film and in which feed rolls advancethe film through a registration station, the feed rolls being driven byan adjustable speed drive and the liquid through which the film ispassed having a temperature control device, the combination withregistration station guides that hold two film strips in superimposedrelation with one another, retractable pins at the registration station,mechanism for moving registration pins into position to compelregistration of successive superimposed film frame areas, one at a time,as said successive film frame areas pass a predetermined location at theregistration station, said mechanism including an element that displaceseach retractable pin into and out of registration producing positionduring a movement of the superimposed film strips that is substantiallyless than the length of a film frame area of said film strips.

'7. In film treating apparatus of the class wherein a sprocket with filmengaging teeth is retracted at a predetermined speed and the shorter ofthe film is pulled through a tank of liquid ahead of the sprocket toincrease th film length and make the spacings of the sprocket openingscorrespond with those of the other film, and the temperature of theliquid in the tank is controlled in accordance with the speed of thesprocket, the combination in said sprocket of angularly spaced teeth inposition to engage sprocket openings of the superimposed motion picturefilms, at least some of the sprocket teeth being of a cross section thatfits fully into the sprocket openings for compelling registration ofcorresponding frame areas of the films, mechanism for projecting andretracting the teeth that fit fully into the sprocket openings, saidmechanism including an element that displaces each retract-- able toothinto and out of registration producing position during a peripheral arcof movement of the sprocket substantially less than the length of a filmframe area of said films.

8. In apparatus for stripping or imbibition printing of motion picturefilms having sprocket teeth openings, and in which one of the films ispulled through a liquid tank and both films are advanced at the samespeed by feed rollers, the liquid tank having a temperature controldevice coordinated with the speed of the feed rolls for causing the filmthat passes through the tank to be increased in length until thespacings of its sprocket tooth openings are equal to those of the otherfilm, and the film frame areas of the respective films are brought intosuperimposed re lation with one another at a registration station, thecombination with said registration station of a sprocket at the station,guide means ahead of and beyond the registration station in position tohold at least one of the films substantially tangent to the sprocket asthe films move toward and be-- yond the sprocket, guide means holdingthe films against the sprocket, angularly spaced teeth around theperiphery of the sprocket in position to engage with the sprocket toothopenings of the films, some of the sprocket teeth fitting freely intoopenings of the films and others of the sprocket teeth being of a crosssection that fits fully into the openings to compel accurateregistration of the corresponding film frame areas of the respectivefilms, bearings located in the sprocket and in which the full fit teethare radially movable to project and retract these teeth with respect tothe film openings, and cam means associated with the movable teeth ofthe sprocket, said cam means having an effective displacement zonesubstantially less than the length of the individual frame areas of thefilm.

9. In film treating ap aratus in which films having corresponding toothopenings are brought into superimposed relation with one another, andguides holding the superimposed stri s substantially tangent to asprocket that advances the superimposed film stri s, the improvementthat comprises teeth at angularly spaced. locations around the peripheryof the s rocket in position to engage the openings in the films, atleast some of the sprocket teeth being of a cross section to fit fullythe film openings to compel accurate registration of corres onding frameareas of the films, the full fit teeth being movable radially withrespect to the sprocket. apparatus for advancing and retracting theteeth in timed relation with rotation of the sprocket, said apparatusincluding an element that displaces and retracts each retractable pininto registration producing position during a movement of thesuperimposed films that is substantially less than the length of a filmframe area of said films, and guides ahead of and beyond the sprocket inposition to hold at least one of the films substantially tangent to thesprocket and to hold both of the films in contact with one another afterthey pass beyond the sprocket without affecting the registrationimparted to the films by the retractable teeth of the sprocket, thediameter of said sprocket being coordinated. with the tooth spacing sothat the next successive tooth of the sprocket enters a film openingbefore each tooth has withdrawn entirely from the preceding film openingthat it engaged.

10. In stripping or imbibition printing, apparatus of the class whereinmotion picture films having sprocket tooth openings for treating, andone -lm is treated to change its length so that the spacings of itssprocket tooth openings correspond with the spacings of the sprocketopenings of another film before the films are brought together insuperimposed relation at a registration station, the combination withsaid registration station of a sprocket located at the registrationstation, teeth on the sprocket angularly spaced around the periphery ofthe sprocket, at least some of the teeth being of a cross section to fitfully into the sprocket tooth openings of the films for compelling exactregistration of the corresponding frame areas of the respective films,mechanism for moving the full fit teeth with respect to the periphery ofthe sprocket to project the teeth into the film openings and to retractthe teeth from the film openings, said mechanism including an elementthat displaces and retracts each full fitting tooth into and out ofregistration producing position during a movement of the superimposedfilms that is substantially less than the length of a film frame area ofsaid films, guide means that hold at least one of the filmssubstantially tangent to the sprocket and other guide means that holdboth of the films in contact with one another beyond the sprocketwithout affecting the registration imparted to the films by theretractable teeth of the sprocket, said other guide means extending fora substantial distance beyond the sprocket without abrupt change indirection so that there is ample time for the softening of an emulsionband or the inbibing of dye before the superimposed films are requiredto make an abrupt turn in their direction of travel.

11. Film stripping apparatus for film strips that have sprocketopenings, said apparatus comprising guide means that bring the filmstrips into initial contact with one another, a registration stationimmediately beyond the region at which the film strips are brought intocontact with one another, a sprocket at the registration station withteeth, at least some of which are movable to proiect them into thesprocket openings and retract them from the sprocket openings inaccordance with a predetermined cycle, the retractable teeth being of across section. to fit fully in the sprocket openings of the film stripswhen the teeth are completely engaged with the sprocket openings, guidemeans holding the strips tangent to the sprocket, the diameter of saidsprocket being coordinated with the tooth spacing of the sprocket sothat the next successive tooth of the sprocket enters a film openingbefore each tooth has withdrawn entirely from the preceding film openingthat it engaged.

ARTHUR J. MILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,016,083 Ensign et a1 Oct. 1,1935 2,071,878 Huc Feb. 23, 1937 2,200,086 Kellogg May '7, 19402,415,442 Rackett Feb. 11, 1947 2,417,060 Capstaif Mar. 11, 1947 FOREIGNPATENTS Number Country Date 89,630 Austria Jan. 15, 1922

